Coronary bypass implant

ABSTRACT

A method and apparatus for performing coronary artery bypass surgery establishes a channel leading directly from a chamber of a heart into a coronary artery. The coronary artery bypass procedure may be performed with or without cardiopulmonary bypass.

The present application is a continuation of and commonly assigned U.S.patent application Ser. No. 08/689,773 filed Aug. 13, 1996 entitled"Method And Apparatus For Performing Coronary Artery Bypass Surgery" andfiled in the name of the same inventors as the present application. Thepresent application also discloses and claims subject matter disclosedin commonly assigned and concurrently filed U.S. patent application Ser.No. 09/054,815 entitled "Closed Chest Coronary Bypass" (filed in thename of the same inventors as the present application and filed as acontinuation application of U.S. patent application Ser. No. 08/689,773)(now U.S. Pat. No. 5,755,682).

I. BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method and apparatus forperforming a coronary artery bypass procedure. More particularly, thepresent invention performs a coronary artery bypass utilizing a numberof approaches including an open-chest approach (with and withoutcardiopulmonary bypass), a closed-chest approach under direct viewingand/or indirect thoracoscopic viewing (with and without cardiopulmonarybypass), and an internal approach through catheterization of the heartand a coronary arterial vasculature without direct or indirect viewing(with and without cardiopulmonary bypass).

2. Description of the Prior Art

Coronary artery disease is the leading cause of premature death inindustrialized societies. But the mortality statistics tell only aportion of the story; many who survive face prolonged suffering anddisability.

Arteriosclerosis is "a group of diseases characterized by thickening andloss of elasticity of arterial walls." DORLAND'S ILLUSTRATED MEDICALDICTIONARY 137 (27th ed. 1988). Arteriosclerosis "comprises threedistinct forms: atherosclerosis, Monckeberg's arteriosclerosis, andarteriolosclerosis." Id.

Coronary artery disease has been treated by a number of means. Early inthis century, the treatment for arteriosclerotic heart disease waslargely limited to medical measures of symptomatic control. Evolvingmethods of diagnosis, coupled with improving techniques ofpost-operative support, now allow the precise localization of theblocked site or sites and either their surgical re-opening or bypass.

The re-opening of the stenosed or occluded site can be accomplished byseveral techniques. Angioplasty, the expansion of areas of narrowing ofa blood vessel, is most often accomplished by the intravascularintroduction of a balloon-equipped catheter. Inflation of the ballooncauses mechanical compression of the arteriosclerotic plaque against thevessel wall. Alternative intravascular procedures to relieve vesselocclusion include atherectomy, which results in the physical desolutionof plaque by a catheter equipped (e.g. a cutting blade or high-speedrotating tip). Any of these techniques may or may not be followed by theplacement of mechanical support and called a "stent," which physicallyholds the artery open.

Angioplasty, and the other above-described techniques (although lessinvasive than coronary artery bypass grafting) are fraught with acorrespondingly greater failure rate due to plaque reformation.Contemporary reports suggest re-stenosis is realized in as many as 25 to55 percent of cases within 6 months of successful angioplasty. See BojanCercek et al., 68 AM. J. CARDIOL. 24C-33C (Nov. 4, 1991). It ispresently believed stenting can reduce the re-stenosis rate.

A variety of approaches to delay or prevent re-blockage have accordinglyevolved. One is to stent the site at the time of balloon angioplasty.Another is pyroplasty, where the balloon itself is heated duringinflation. As these alternative techniques are relatively recentinnovations, it is too early to tell just how successful they will be inthe long term. However, because re-blockage necessitates the performanceof another procedure, there has been renewed interest in the clearlylonger-lasting bypass operations.

The current indications for coronary artery bypass grafting have beenoutlined. See LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIALREVASCULARIZATION: INDICATIONS, SURGICAL TECHNIQUES AND RESULTS 4-5(1990). Criteria vary dependent upon whether the intent is therapeutic(that is, to reverse cardiac compromise in the patient currentlysuffering symptoms), or prophylactic (that is, to prevent a potentiallyfatal cardiac event from occurring in someone who is, at present,symptom free). Id.

The traditional open-chest procedure requires an incision of the skinanteriorly from nearly the neck to the navel, the sawing of the sternumin half longitudinally, and the spreading of the ribcage with amechanical device to afford prolonged exposure of the heart cavity. Ifboth lungs are deflated, a heart-lung, or cardiopulmonary bypassprocedure, is also necessary.

Depending upon the degree and number of coronary vessel occlusions, asingle, double, triple, or even greater number of bypass procedures maybe necessary. Often each bypass is accomplished by the surgicalformation of a seperate conduit from the aorta to the stenosed orobstructed coronary artery, at a location distal to the diseased site. Amajor obstacle has been the limited number of vessels that are availableto serve as conduits. Potential conduits include the two saphenous veinsof the lower extremities, the two internal thoracic arteries under thesternum, and the single gastroepiploic artery in the upper abdomen.Theoretically, if all of these vessels were utilized, the procedurewould be limited to a quintuple (5-vessel) bypass. Because of this,newer procedures using a single vessel to bypass multiple sites haveevolved. However, this technique is fraught with its own inherenthazards, though. When a single vessel is used to perform multiplebypasses, physical stress (e.g., torsion) on the conduit vessel canresult. Such torsion is particularly detrimental when this vessel is anartery.

Unfortunately, attempts at using vessels from other species(xenografts), or other non-related humans (homografts) has been largelyunsuccessful. See LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FORMYOCARDIAL REVASCULARIZATION: INDICATIONS, SURGICAL TECHNIQUES ANDRESULTS 38-39 (1990). Similarly, trials with synthetic alternatives havenot been encouraging. See Id. at 39.

While experimental procedures transplanting alternative vessels continueto be performed, in general clinical practice there are five vesselsavailable to use in this procedure over the life of a particularpatient. Once these "spare" vessels have been sacrificed, there islittle or nothing that modern medicine can offer. It is unquestionablethat new methods, not limited by the availability of such conduitvessels, are needed.

In the past, the normal contractions of the heart have usually beenstopped during suturing of the bypass vasculature. This can beaccomplished by either electrical stimulation which induces ventricularfibrillation, or through the use of certain solutions, calledcardioplegia, which chemically alter the electrolytic milleausurrounding cardiac muscles. Stoppage of the heart enhancesvisualization of the coronary vessels, while removing the need for bloodflow through the coronary arteries during the procedure. This providesthe surgeon with a "dry field" in which to operate and create afunctional anastomosis. After the coronary artery bypass procedure iscompleted, cardioplegia is reversed, and the heart electricallystimulated if necessary. As the heart resumes the systemic pumping ofblood, the cardiopulmonary bypass is gradually withdrawn. The seperatedsternal sections are then re-joined, and the overlying skin andsaphenous donor site or sites (if opened) are sutured closed.

The above-described procedure is highly traumatic. Immediatepost-operative complications include infection, bleeding, renal failure,pulmonary edema and cardiac failure. The patient must remain intubatedand under intensive postoperative care. Narcotic analgesia is necessaryto alleviate the pain and discomfort.

The most troubling complication, once the immediate post-surgical periodhas passed, is bypass vessel re-occlusion. This has been a particularproblem with bypass grafting of the left anterior descending coronaryartery when the saphenous vein is employed. Grafting with the internalthoracic (internal mammary) artery results in long-term patency ratesuperior to saphenous vein grafts, particularly when the left anteriordescending coronary artery is bypassed. Despite this finding, somecardiothoracic surgeons continue to utilize the saphenous vein becausethe internal thoracic artery is smaller in diameter and more fragile tomanipulation; thus making the bypass more complex, time-consuming, andtechnically difficult. Additionally, there are physiologicalcharacteristics of an artery (such as a tendency to constrict) whichincreases the risk of irreversible damage to the heart during theimmediate period of post-surgical recovery.

Once the patient leaves the hospital, it may take an additional five toten weeks to recover completely. There is a prolonged period duringwhich trauma to the sternum (such as that caused by an automobileaccident) can be especially dangerous. The risk becomes even greaterwhen the internal thoracic artery or arteries, which are principlesuppliers of blood to the sternum, have been ligated and employed asbypass vessels.

Due to the invasive nature of the above technique, methods have beendevised which employ contemporary thoracoscopic devices andspecially-designed surgical tools to allow coronary artery bypassgrafting by closed-chest techniques. While less invasive, all but themost recent closed-chest techniques still require cardiopulmonarybypass, and rely on direct viewing by the surgeon during vascularanastomoses. These methods require a very high level of surgical skilltogether with extensive training. In such situations, the suturing ofthe bypassing vessel to the coronary artery is performed through a spacecreated in the low anterior chest wall by excising the cartilaginousportion of the left fourth rib. Also, as they continue to rely on theuse of the patient's vessels as bypass conduits, the procedures remainlimited as to the number of bypasses which can be performed. Because ofthese issues, these methods are not yet widely available.

In view of the above, it would be desirable to provide other methods ortechniques by which adequate blood flow to the heart could bere-established which do not rely on the transposition of a patient's ownarteries or veins. It would also be desirable to provide other methodsor techniques by which adequate blood flow to the heart could bere-established which results in minimal tissue injury. It would beparticularly desirable if such methods or techniques did not requireopening of the chest by surgical incision of the overlying skin and thedivision of the sternum. It would be even more desirable if such methodsor techniques did not require surgical removal of cartilage associatedwith the left fourth rib, did not require the surgical transection ofone or both internal thoracic arteries, did not require the surgicalincision of the skin overlying one or both lower extremities, and didnot require the surgical transection and removal of one or bothsaphenous veins. It would also be desirable if such methods ortechniques could be performed without stoppage of the heart, and withoutcardiopulmonary bypass.

The conventional surgical procedures (such as those described above) forcoronary artery bypass grafting using saphenous vein or internalthoracic artery via an open-chest approach have been described andillustrated in detail. See generally Stuart W. Jamieson, AortocoronarySaphenous Vein Bypass Grafting, in ROB & SMITH'S OPERATIVE SURGERY:CARDIAC SURGERY, 454-470 (Stuart W. Jamieson & Norman E. Shumway eds.,4th ed. 1986); LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIALREVASCULARIZATION: INDICATIONS, SURGICAL TECHNIQUES AND RESULTS 48-80(1990). Conventional cardiopulmonary bypass techniques are outlined inMark W. Connolly & Robert A. Guyton, Cardiopulmonary Bypass Techniques,in HURST'S THE HEART 2443-450 (Robert C. Schlant & R. Wayne Alexandereds., 8th ed. 1994). Coronary artery bypass grafting, utilizingopen-chest techniques but without cardiopulmonary bypass, is describedin Enio Buffolo et al., Coronary Artery Bypass Grafting WithoutCardiopulmonary Bypass, 61 ANN. THORAC. SURG. 63-66 (1996)

Some less conventional techniques (such as those described above) areperformed by only a limited number of appropriately skilledpractitioners. Recently developed techniques by which to perform acoronary artery bypass graft utilizing thoracoscopy andminimally-invasive surgery, but with cardiopulmonary bypass, aredescribed and illustrated in Sterman et al., U.S. Pat. No. 5,452,733(1995). An even more recent coronary artery bypass procedure employingthoracoscopy and minimally-invasive surgery, but without cardiopulmonarybypass, is described and illustrated by Tea E. Acuff et al., MinimallyInvasive Coronary Artery Bypass Grafting, 61 ANN. THORAC. SURG. 135-37(1996).

Methods of catheterization of the coronary vasculature, techniquesutilized in the performance of angioplasty and atherectomy, and thevariety of stents in current clinical have been described andillustrated. See generally Bruce F. Waller & Cass A. Pinkerton, ThePathology of Interventional Coronary Artery Techniques and Devices, in 1TOPOL'S TEXTBOOK OF INTERVENTIONAL CARDIOLOGY 449-476 (Eric J. Topoled., 2nd ed. 1994); see also David W. M. Muller & Eric J. Topol,Overview of Coronary Athrectomy, in 1 TOPOL'S TEXTBOOK OF INTERVENTIONALCARDIOLOGY at 678-684; see also Ulrich Sigwart, An Overview ofIntravascular Stents: Old & New, in 2 TOPOL'S TEXTBOOK OF INTERVENTIONALCARDIOLOGY at 803-815.

Finally, some techniques remain in the experimental stages, and arelimited to animal testing. Direct laser canalization of cardiacmusculature (as opposed to canalization of coronary artery feeding thecardiac musculature) is described in Peter Whittaker et al., TransmuralChannels Can Protect Ischemic Tissue: Assessment of Long-term MyocardialResponse to Laser- and Needle-Made Channels, 94(1) CIRCULATION 143-152(Jan. 1, 1996).

II SUMMARY OF THE INVENTION

According to the present invention, a method and apparatus forsurgically bypassing an obstructed coronary artery or arteries relies onthe establishment of a channel or channels leading directly from achamber of the heart into the obstructed coronary artery or arteries ata site or sites distal to the obstruction. At the time of, or prior tothe procedure, coronary arterial obstruction can be identified throughangiography. Standard angiographic techniques utilize radio-opaque dyesintroduced into the coronary arterial vasculature to identify defects inblood flow by standard radiological techniques. Standard radiologicaltechniques involve visualization of flow defects through the taking ofX-rays or viewing under fluoroscopy at the time that a radio-opaque dyeis injected. Alternatively, a video recording system may be enlisted torecord these fluoroscopic images, and allow the identification of moresubtle defects through repeated viewings. At the time of, or prior tothe procedure, a site or sites for the coronary artery bypass procedurecan thus be selected.

The present invention is particularly useful for coronary artery bypassprocedures in a patient suffering from obstructive coronary arterydisease. The methods can be performed while the patient is anesthetized.Anesthesia may be, but is not limited to, general anesthesia. Thepresent permits an array of procedures of varying invasiveness. As inother procedures, the level of anesthesia necessary is expected to varydirectly with the invasiveness of the surgery. The present invention,because it minimizes normal tissue damage, is especially useful forcoronary artery bypassing in a patient who, because of other medicalproblems such as chronic respiratory failure, must be maintained at ahigher level of consciousness than that usually realized during standardgeneral anesthesia. In such a patient, a less invasive approach may bechosen. As in any major surgical procedure, the patient's heart andrespiratory rates, peripheral oxygenation, urinary output, and otherbodily functions may be monitored. During some or all of the bypass,cardiac contractions can be slowed, or stopped, to both improvevisualization of the coronary vasculature, and to reduce the oxygenrequirements of cardiac muscle. An intra-esophageal probe or probes, orother appropriately-placed probe or probes to monitor the cardiac cycle,and to trigger power to the intraventricular laser when utilized, may beadvantageous.

The present invention can be performed in an operating room equippedwith standard X-ray, and/or fluoroscopy, and/or cine-fluoroscopyequipment, as is standardly utilized during cardiac catheterizationprocedures. The present invention can be performed while the treatingphysician or physicians view the X-rays, and/or fluoroscopic imagesproduced during the procedure, as is standardly done during cardiaccatheterization.

The present invention avoids the previous limitations on the number ofperformable bypass procedures. Due to the limited number of arteriesand/or veins available, standard procedures become increasingly risky torepeat. Rather than relying on harvested veins and arteries as bypassconduits, the present invention forms a channel (or conduit) which leadsdirectly from a chamber of a patient's heart into a coronary artery at asite distal to the obstruction or narrowing.

In the most preferred embodiment, the left ventricle is the chamber ofthe heart utilized. There are two reasons for this selection. First, theleft ventricle normally provids blood to the coronary arteries, becauseit pumps blood into the aorta from which the coronary arteries branch.Therefore, the blood pressure peak generated by the left ventricle ismost similar to the blood pressure peak the proximal coronary arterywould normally experience. Second, the blood which flows into the leftventricle is returning from the the lungs. In the lungs the bloodacquires oxygen and loses carbon dioxide. Thus, the blood available byshunting from the chambers of the left side of the heart will have ahigher oxygen and lower carbon dioxide content then that blood withinthe right-sided heart chambers.

The Open-Chest Procedure

As a first step, the patient can be prepared in the usual fashion foropen-chest cardiac bypass surgery. Once access to the heart and coronaryvasculature is gained, cardiopulmonary bypass and stoppage of the heartmay, but is not necessarily, performed.

As a second step, blood flow through the coronary artery to be bypassedis stopped. One example by which blood flow can be stopped is byclamping the artery proximal to the chosen bypass site. Another exampleby which blood flow can be discontinued is by forming a loop around theartery with suture and applying traction.

As a third step, an incision is formed in the artery at a site distal tothe narrowing or obstruction. A channel is then formed leading from acoronary artery through the wall of the coronary artery, through theunderlying cardiac muscle and into a chamber of a heart. One example bywhich such a channel could be formed is by laser ablation of theintervening tissue, another example is by forming an incision with anelectrosurgical tool which will simultaneously cut and cauterize theintervening tissue, and yet another example is by blunt dissection withan appropriate blunt tool such as an awl punch or trocar.

As a fourth step, one arm of an appropriately dimensioned apparatus ofthe present invention is inserted through this channel leading into thechamber of the heart. The remaining arm or arms of the apparatus arethen seated within the lumen of the coronary artery.

Depending on the relationship over time of the pressures present withinthe chamber of the heart as compared to the pressures realized withinthe coronary artery at the bypass location, a check valve permittingunidirectional blood flow from the chamber of the heart into thecoronary artery may be associated with the apparatus. The use of a checkvalve, and the opening pressure of such a valve when employed, can beindividually determined through selective catheterization of thecoronary artery and the chamber of the heart either prior to, or at thetime of, the bypass procedure. See Minoru Hongo et al., Effects of HeartRate on Phasic Coronary Blood Flow Pattern and Flow Reserve in Patientswith Normal Coronary Arteries: A study with an Intravascular DopplerCatheter and Spectral Analysis, 127(3) AM. HEART J. 545-51 (March 1994)(outlining newer techniques by which pressures within the coronaryartery can be measured during the normal cardiac cycle). Simultaneouselectrocardiography may also be useful in this regard. Suchcatheterization and blood pressure measurements performed in concertwith stress testing and electrocardiography can be utilized to determinewhat minimal pressures are necessary within the bypassed coronary arteryto produce adequate blood flow at rest and during stress. Correlation ofthe pressure necessary within the coronary artery to that present withinthe chambers of the heart can be used to establish the appropriatechamber of the heart to utilize. In the most preferred embodiment, theleft ventricle is anticipated.

As a fifth step, the coronary artery incision is closed in the usualfashion. One example of closure is re-approximating the walls of thecoronary artery with suture, while another example is closure of thewalls by staples which interlock with the underlying device of thepresent invention.

As a sixth step (if needed), cardiac contractions are reinitiated. Oneexample by which cardiac contractions are commonly reinitiated isthrough electrical defibrillation, while another example is through thereversal of cardioplegia by standard techniques. Cardioipulmonarybypass, if utilized, can then be slowly discontinued.

As a seventh step, the pericardium, sternum, and overlying skin can thenbe re-approximated and sutured and/or stapled closed, as is standardlyperformed following open-chest surgery.

The Closed-Chest Procedure

In another embodiment, the method and apparatus of the present inventionreduces trauma to normal tissue, limits blood loss, and lowers the riskof infection heretofore associated with standard coronary artery bypassprocedures. In this embodiment, the procedure is performed under directand indirect viewing through a space (i.e., window) formed in the leftanterior chest wall, as well as viewed through a thoracoscope. In thisembodiment, the surgery is performed through the formed window via aseries of access trocar sheaths, which allow the introduction ofsurgical instruments. See Sterman et al., U.S. Pat. No. 5,452,733(1995). See, also Acuff et al., Minimally Invasive Coronary ArteryBypass Grafting, 61 ANN. THORAC. SURG. 135-37 (1996). The basic steps ofthe procedure are similar to the open-chest technique outlined above.The location of the bypass site, the requirement for adequatevisualization, and the overall health of the particular patient arefactors likely to contribute to the decision as to which procedure toemploy.

The Catheterization Procedure

The method and apparatus of the present invention, in yet anotherembodiment, greatly minimizes damage to normal tissue, although at theexpense of the (at least partial) loss of direct visualization, byperforming the coronary bypass surgery via catheterization. In thisembodiment, the entire procedure is limited to two incisions: one in thegroin and one in the right superior-anterior chest. Catheter access tothe coronary arterial vasculature and chambers of the heart are achievedthrough these incisions.

As a first step, the obstructed coronary artery is catheterized byintroduction of a catheter into the innominate or femoral artery and bythe feeding of the catheter retrograde through the ascending aorta andinto the obstructed artery via standard catheterization techniques. Ifthe obstruction does not allow passage of the catheter past the site orsites of obstruction, the catheter can be removed, and angioplasty,atherectomy, or another appropriate procedure can be performed. Once thecatheter is positioned distally to the site of the obstruction, a stentis secured to the arterial wall at the preselected bypass site. This canbe accomplished by inflation of a balloon circumferentially attached tothe catheter. This stent provides the appropriate structural strength toensure continued integrity of the coronary artery, following opening ofthe coronary arterial wall. Once this stent has been placed, thecatheter is withdrawn and allowed to rest within the ascending aorta.

As a second step, a chamber of a heart is catheterized. The left side ofthe heart, including the left auricle and left ventricle, can becatheterized by introduction of a penetration means (e.g., laser orradiofrequency) equipped catheter into the innominate or femoral arteryand by the feeding of said catheter retrograde through the ascendingaorta and into said left auricle or left ventricle via standardcatheterization techniques. In the preferred embodiment, the leftventricle is catheterized in this manner. In one embodiment, a channel,leading from one of the chambers of the left side of a heart andcontinuing through the deep arterial wall of a coronary artery, at asite consistent with the previously-placed intracoronary stent, iscreated by laser or radiofrequency ablation, or like techniques, whilebeing viewed through standard radiologic techniques. Once this channelappears to have been created, radio-opaque dye can be injected into thechannel via a port on the intraventricular catheter. Once thisradio-opaque dye, visualized by standard angiographic techniques, isseen to flow into the coronary artery at the chosen bypass site,ablation or like techniques of the heart chamber wall is discontinued.

As a third step, the catheter, which is at rest within the ascendingaorta, is re-inserted into the coronary artery and advanced understandard radiologic visualization until it is again located at the siteof the previously-placed intracoronary stent. The balloon on the tip ofthe catheter is then re-inflated. The inflation of this balloon servestwo purposes. First, in the case where there is no cardiopulmonarybypass, the inflation of this catheter prevents blood from flowing fromthe coronary artery, through the channel formed in the second stepdescribed above, and into a chamber of the heart. To facilitate thesupply of blood to the microcirculation normally fed by the coronaryartery being bypassed, there are channels within the proximal and distalaspects of the intracoronary catheter. These channels allow blood withinthe coronary artery to enter the catheter upstream from the balloon andto flow within the catheter downstream and exit from the catheterthrough channels located within the catheter but distal to the balloon.The second function served by inflation of this balloon is as a physicalstop for the intraventricular catheter located within the formedchannel, as outlined below.

As a fourth step, the intraventricular catheter is advanced to come torest against the wall of the inflated balloon located on the tip of theintracoronary catheter. A balloon located on the distal tip of theintraventricular catheter is then inflated. Inflation of this balloonresults in the seating of a an apparatus which circumferentiallysurrounds this balloon against the walls of the formed channel. In oneembodiment, this device can be a spiral sheet. In this embodiment,inflation of the balloon of the intraventricular catheter results inthis spiral sheet being forced into an expanded position; where it takesthe form of a hollow tube. In this embodiment, once this spiral sheet isforced into the form of a hollow tube, an interlocking lip on thisdevice results in the locking of the former spiral sheet into a hollowtube configuration. In another embodiment, the expansion of the balloonon the tip of the intraventricular catheter results not only in theapparatus seating against the walls of the formed channel, it alsoresults in the interlocking of the apparatus with the intracoronarystent previously placed. In either embodiment, the proper positioning ofthe intraventricular catheter tip to facilitate proper positioning ofthe device within the formed channel, and to result in the interlockingwith the intracoronary stent if chosen, can be determined by standardradiologic techniques prior to the inflation of the intraventricularballoon. Once the device is properly postitioned and locked within theformed channel, the balloon on the tip of the intraventricular catheteris deflated. The intraventricular catheter is then withdrawn from thebody.

As a fifth step, a third catheter is inserted into the innominate orfemoral artery and fed retrograde through the ascending aorta and into achamber of the left side of the heart via standard catheterizationtechniques. In a preferred embodiment, the third catheter is advancedinto the left ventricle.

The distal tip of this third catheter holds an apparatus which has theability to be mechanically interlocked with the first apparatus whichwas placed within the formed channel in the fourth step described above.The second apparatus is place within the lumen of the fromed channelthrough manipulation of the intraventricular catheter by standardcatheter-control techniques.

In one embodiment the second apparatus can be secured to the walls ofthe channel itself through stapling, biologically-effective glueing, orthe like. In another embodiment, this second apparatus can beinterlocked with the first apparatus previously placed through variousconventional techniques by which one hollow tube is mechanically lockedto another hollow tube. In one embodiment, this interlocking could takethe form of threading. In another embodiment, this interlocking could beaccomplished by a tongue on the second apparatus that slips into agroove on the first apparatus.

The second apparatus allows blood to flow within the lumen of theapparatus either bidirectionally, or unidirectionally. In oneembodiment, the second apparatus can be equipped with a check valvewhich allows blood to flow from a chamber of a heart into a coronaryartery, while prohibiting blood flow in the opposite direction. In thisembodiment, this flow-restrictive apparatus is placed within thelaser-ablated channel and associated with the previously-placedapparatus.

Once the second apparatus has been located within the formed channel,and either effectively secured to the channel walls, or effectivelysecured to the first apparatus, the second apparatus can be releasedfrom the tip of the third catheter. In one embodiment, properinterlocking of the second apparatus to the first apparatus can beascertained by standard radiographic techniques. In another embodiment,proper interlocking of the second apparatus to the first apparatus canbe indirectly viewed through a remote fiberoptic viewing system, or thelike, inherent to the third catheter. The third catheter is thenwithdrawn from the body.

As a sixth step, blood flow from a chamber of the heart into thebypassed coronary artery and, in cases where a check valve has beenplaced, the corresponding absence of flow from the coronary artery intoa chamber of the heart, can be determined by standard angiographictechniques.

Clarification of Meanings

Living biological organisms react in a range of varying ways to foreignmaterials. The term foreign materials is meant to include all materials,whether biological or non-biological, which are not normally presentwithin that particular subject.

Because subjects respond to foreign materials in a range of variousways, the apparatus of the present invention can be exposed to cells,treated by biological compounds, or exposed to pharmaceutical or otherchemical agents, which reduce the reactions normally resulting whenforeign bodies are internally introduced.

With regard to the specification and claims of this application, thephrase "reduce reaction" is meant to indicate a reduction in tissueresponses. This is meant to include, but not to be limited to, immunereactions, tissue scarring, blood clotting, and the like. The literatureis replete with pharmaceuticals which can be either locally orsystemically administered and which decrease the immune response toforeign bodies. These include corticosteroids, and the like. It is alsowell known in the literature that there are pharmaceutical agents whichreduce scar tissue formation following injury. Newer publishedtechniques to reduce re-stenosis in transplanted artificial vesselsinclude coating such devices with non-immunogenic endothelial cells orfibroblasts. A common problem with transplanted vessels is bloodclotting, and agents which reduce such clotting have been widelyreported.

The phrase "reduce reaction" is also meant to indicate a reduction inthe changes in arterial walls associated with the family of diseasesknown as arteriosclerosis. Arteriosclerosis is the most common cause ofcoronary artery occlusion and/or narrowing. Pharmaceutical agents whichinhibit the formation of arteriosclerotic plaques have been discovered.Coating the device with agents which decrease the accumulation of suchdeposits can be beneficial in the prevention of re-stenosis.

Conclusion

In summary, creating a channel or channels which lead directly from achamber of the heart into the coronary arterial vasculature shoulddecrease the morbidity and mortality of bypass surgery, should reducepost-surgical recovery time, should decrease coronary artery bypassgrafting costs, and should allow the creation of multiple bypass sitesto multiple diseased coronary arteries either simultaneously, or at somelater point in time. In no way is the procedure limited by theavailability and patency of veins or arteries harvested from the bypasspatient. In addition, the invention eliminates the risk of aneurysmaldilitation and subsequent functional deterioration of transplantedsaphenous veins, as well as the risk of arterial constriction andsubsequent functional deterioration of internal thoracic orgastroepiploic arteries, particularly when compared to techniques whichresult in torsion on transplanted artery.

III BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a right anterior superior perspective view of an L-shapedapparatus for use in the present invention.

FIG. 1B is a side elevation view of the apparatus of FIG. 1A shownpartially in section to reveal an optional check valve located in thelumen of the anchor arm of the apparatus.

FIG. 1C is a side elevation view of a apparatus similar to that of FIG.1A showing the addition of a capacitance pressure reservoir as analternative embodiment.

FIG. 2A is a right anterior superior perspective view of a T-shapedapparatus for use in the present invention.

FIG. 2B is a side elevation view of the tube of FIG. 2A shown partiallyin section to reveal an optional check valve located in the lumen of theanchor arm of the apparatus.

FIG. 2C is a side elevation view of the tube of FIG. 2A shown partiallyin section to reveal one optional check valve located in the lumen ofthe anchor arm of the apparatus, and another optional check valvelocated in one of the intracoronary arms of the apparatus.

FIG. 2D is a side elevation view of a apparatus similar to that of FIG.2A showing the addition of a capacitance pressure reservoir as analternative embodiment.

FIG. 3A is a partial side elevation view of an apparatus similar to thatof FIGS. 1A and 2A shown partially in section to reveal a flexibleanchor arm with rigid rings ensheathed in a flexible covering as analternative embodiment.

FIG. 3B is a partial side elevation view of an apparatus similar to thatof FIG. 3A shown in section in an extended form.

FIG. 3C is is a partial side elevation view of an apparatus similar tothat of FIG. 3A shown in section in a compressed form.

FIG. 4 is an anterior view of a human chest which is incisedlongitudinally to reveal a dissected pericardium, and mediastinalcontents.

FIG. 5 is a magnified view of area circled 200 in FIG. 4 illustrating alongitudinally incised coronary artery.

FIG. 6 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating a channel leadingfrom the lumen of a coronary artery and into a chamber of the heartaccording to the methods of the present invention.

FIG. 7 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the partialplacement of one embodiment of the device of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6.

FIG. 8 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the completedplacement of one embodiment of the device of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6.

FIG. 9 is a partial external perspective view of a sutured coronaryartery and phantom view of the device of the present invention.

FIG. 10 is a schematic illustration of the use of an endovascularcatheter to catheterize the patient's coronary artery.

FIG. 11A is a cutaway side elevation view of the coronary artery of thebypass procedure illustrating the intravascular catheter withdistally-located stent prior to inflation of the catheter balloonunderlying the stent.

FIG. 11B is a cutaway side elevation view of the coronary artery of thebypass procedure illustrating the intravascular catheter withdistally-located stent following inflation of the catheter balloonunderlying the stent.

FIG. 11C is a cutaway side elevation view of a coronary arteryillustrating the stent seated to the walls of the coronary artery andthe catheter partially withdrawn following deflation of the catheterballoon.

FIG. 12 is a schematic illustration with the heart in partial cutaway ofthe use of an endovascular catheter to catheterize the patient's leftventricle.

FIG. 13A is a cutaway view of the left ventricle and a partial cutawayview of the coronary artery with seated stent illustrating the formationof the channel into the wall of the left ventricle.

FIG. 13B is a cutaway view of the left ventricle and a partial cutawayview of the coronary artery with seated stent illustrating the completedchannel through the wall of the left ventricle and deep wall of thecoronary artery at the chosen bypass site.

FIG. 14A is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating theplacement of the second intraventricular catheter within the formedchannel.

FIG. 14B is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating theblockage of the formed channel by the re-inflated balloon of theintracoronary catheter.

FIG. 14C is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating theinflation of the balloon located on the distal end of theintraventricular catheter and the seating of the overlying spiral-shapeddevice against the walls of the formed channel.

FIG. 14D is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating thedevice in its locked cylindrical shape seated against the channel wallsand the partially withdrawn second intraventricular catheter.

FIG. 15A is a right anterior superior perspective view of the deviceplaced within the formed channel in its spiral shape.

FIG. 15B is a right anterior superior perspective view of the deviceplaced within the formed channel in its cylindrical form.

FIG. 16 is a cross-sectional view of the interlocking mechanism of thedevice of FIGS. 15A and 15B in its locked position.

FIG. 17A is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery, with the device shown in FIGS. 15Aand 15B seated within the formed channel, illustrating the introductionof the third intraventricular catheter into the formed channel.

FIG. 17B is a cross-sectioned view of the left ventricle and a partialcutaway view of the coronary artery, with the device shown in FIGS. 15Aand 15B seated within the formed channel, illustrating the tongue andgroove interlocking of the check-valve equipped device to the deviceseated within the formed channel.

IV DESCRIPTION OF PREFERRED EMBODIMENT

A. The Problem

Heart disease remains the leading cause of death in the industrializedworld. Myocardial infarction, or irreversible damage to cardiac muscle,can result when cardiac musculature is inadequately oxygenated for asufficient period of time. The leading cause of inadequate oxygenationis insufficient blood flow through the coronary arteries which perfusethe cardiac musculature. The most common cause of insufficient bloodflow within the coronary arteries is vascular stenosis or occlusion. Byfar the leading cause of stenosis or occlusion of the coronary arteriesis arteriosclerosis.

Blockage of the coronary vasculature may be reversed by several means.The most durable solution to the problem, though, is coronary arterybypass grafting.

Traditionally, the bypass procedure has entailed forming a new pathwaywhere blood from the aorta is supplied to coronary artery or arteries ata site or sites distal to the obstruction. It is axiomatic that thisform of coronary artery bypass grafting is possible only where suitableconduits are available for transplantation. In general, vesselsharvested from other species (xenografts), as well as those taken fromunrelated subjects of the same species (homografts), have proveninsufficiently durable as transplant conduits. Similarly, transplantswith artificial vessels have been largely unsuccessful. Therefore,coronary artery bypass grafting has been available only to thosesubjects who posess suitable transplant vessels, and who are physicallyable to withstand the harvesting and transplantation of one or more ofthese vessels across their coronary vasculature.

B. The Invention

The invention departs from the traditional bypass approach. Rather thenproviding an alternative pathway for blood to flow from an aorta to acoronary artery, the invention provides a blood flow path leadingdirectly from a chamber of a heart to a coronary artery, at a sitedownstream from the stenosis or occlusion. The surgical placement of theapparatus of the present invention establishes this alternative pathway.

C. Embodiments with the Open Chest Approach

1. The Apparatus of the Present Invention for Use in the Open ChestApproach

As will be more fully described, the present invention places anapparatus for defining a blood flow conduit directly from a chamber of aheart to a coronary artery downstream of an occluded site. Beforedescribing the surgical methods for placing such an apparatus, anapparatus of the present invention will be described. The purpose of thefollowing description is to clarify an understanding of the novelsurgical procedures using such an apparatus.

The apparatus of the present invention can be a variety of shapes orsizes, and is not meant to be limited as to size, shape, construction,material, or in any other way by the following examples in which aprefered embodiment is illustrated.

With initial reference to FIGS. 2A, 2B, 2C, 2D and 2E, an embodiment ofan apparatus according to the present invention is shown as a T-shapedstent 10. The stent 10 is hollow, and includes two axially-alignedintracoronary arms 14, 16 terminating at open ends 14a, 16a. An anchorarm 12 (having an open end 12a) extends perpendicularly to arms 14, 16.The entire stent 10 is hollow to define a blood flow conduit 11providing blood flow communication between open ends 12a, 14a and 16a.

As will be more fully discussed, arms 14 and 16 are adapted to be placedand retained within a lumen of a coronary artery on a downstream side ofan occlusion with open ends 14a, 16a in blood flow communication withthe lumen. The anchor arm 12 is adapted to extend through and beretained in a heart wall (e.g., a wall of the left ventricle) with theopen end 12a in blood flow communication with blood within the chamber.Accordingly, when so placed, the stent 10 defines a surgically-placedconduit establishing direct blood flow from the heart chamber to theartery. By "direct" it is meant that the blood flow does not passthrough the aorta as occurs in traditional bypass procedures.

FIG. 2B illustrates use of an optional check valve 22 within the stent10 and positioned in anchor arm 12. Check valves are well known andvalve 22 permits flow only in the direction of arrow A (i.e., from openend 12a to open ends 14a, 16a) while blocking reverse flow. Valve 22 isused to prevent the back-flow of blood from the coronary artery to theheart chamber. Valves sufficiently small to fit into arm 20 are withinthe skill of the art. For example, Wanpen Vongpatanasin et. al,Prosthetic Heart Valves, 335(6) N.E.J.M. 407-416 (Aug. 8, 1996)describes valves of 24 square millimeters.

FIG. 2C illustrates the use of check valve 22 as well as a second checkvalve 26 in arm 16 near the open end 16a of the apparatus. The secondcheck valve 26 permits blood flow only in the direction of arrow B.Valve 26 is used to prevent the back flow of blood in an upstreamdiretion within the coronary artery. For example, the coronary arterymay not be completely obstructed and may have a reduced flow past anobstruction. The use of the T-stent 10 with axially alligned arms 14, 16takes advantage of such reduced flow and supplements such flow withblood through anchor arm 12. As will be described, the stent 10 isplaced with the arms 14, 16 in the lumen of the artery with opening 16apositioned on the upstream side (i.e., nearest to, but still downstreamof, the obstruction). Thus, valve 26 permits the utilization of normalblood flow while blocking back-flow.

While a T-shaped stent 10 is presently anticipated as most desirable, anL-shaped stent 10' (FIGS. 1A, 1B, 1C) may be used to completely bypassthe coronary obstruction. An L-shaped stent 10' has an anchor arm 12'with an open end 12a'. Unlike stent 10, stent 10' has only oneintracoronary arm 14' perpendicular to arm 12'. Arm 14' has an open end14a' and stent 10' is hollow to define a continuous fluid pathway orconduit 11' from end 12a' to end 14a'. In application, arm 14' is placedwithin the lumen of an artery. End 14a' faces downstream from anobstruction. Arm 12' is placed through the heart wall with end 12a' influid communication with blood within the heart chamber. As illustratedin FIG. 1B, the anchor arm 12' can include a check valve 22' similar tovalve 22 of stent 10.

Stent 10, 10' may be rigid, or have varying flexibilities. FIGS. 3A, 3Band 3C demonstrate one embodiment where the anchor arm (i.e., elements12, 12' of FIGS. 1A and 2A) is comprised of a number of rings 17surrounded by a membrane 18. In FIGS. 3A-3C, only anchor arm 20 isshown. It will be appreciated that anchor arm 20' may be identicallyconstructed. In the embodiment of FIGS. 3A-3C, the rings 17 can beconstructed of teflon, and the surrounding membrane 18 can beconstructed of a double-walled dacron sheath into which the teflon rings17 are sewn. In this embodiment, the rings 17 provide structuralstrength. The structural strength maintains an open lumen or conduit 11leading into the coronary artery by preventing the conduit 11 fromcollapsing by reason of contraction of the heart muscle surrounding theanchor arm 12. The series of rings 17 provide a degree of flexibilitywhich allows a channel formed through the heart chamber muscular wall(receiving anchor arm 12) to be angled or curved. In addition, theflexability of the surrounding sheath 18 in concert with the rigid rings17 will allow the anchor arm 12 to expand, FIG. 3B, and contract, FIG.3C, with the contractions and relaxations of the surrounding cardiacmusculature.

It should be noted that, because of the semi-rigid nature of the anchorarm 12 constructed in this manner, a method of attaching that end of theanchor arm in contact with the inner surface of a chamber of a heart canbe useful. In the example illustrated, this attaching mechanism 19 is arigid teflon flange. It will be appreciated that other mechanisms ofattachment, such as suturing, biologically glueing, etc. are alternativeoptions.

The apparatus of the present invention (as thus described) provides apath 11 through which blood flows from a chamber of a heart and into acoronary artery. Additionally, such a device can store blood underpressure for a period of time prior to its introduction into a coronaryartery. As depicted in the embodiments of FIGS. 1C and 2D, this aspectof the apparatus 10, 10' of the present invention is referred to as acapacitance pressure reservoir (CPR) 24, 24'.

It is well known from the literature that blood flow through the normalcoronary artery is cyclical. Blood flow is increased during diastole(when the heart muscle is in a relaxing state), and decreases orreverses during systole (when the heart muscle is in a contractingstate). See, e.g., F. Kajiya et al., Velocity Profiles and Phasic FlowPatterns in the Non-Stenotic Human Left Anterior Descending CoronaryArtery during Cardiac Surgery, 27 CARDIOVASCULAR RES. 845-50 (1993).

The pressure gradient across the lumens 12a, 12a', 14a', 16a of theapparatus 10, 10' of the present invention will vary over the cardiaccycle. For example, during systole, the contraction of the heart muscleswill generate high relative pressures within the left ventricle. Thepressures within the coronary arterioles and capillaries distal to thebypass site are also high during this time, due to the externalcompression of the contracting cardiac musculature surrounding thesevessels. This is particularly true for the vessels of themicrocirculation deep within the heart which serve the endocardium. Theoptional CPR 24, 24' stores the pressurized blood during systole fordelivery to the heart muscles via the coronary circulation duringdiastole when pressures are reduced. In essence, the CPR 24, 24' servesa function similar to the elastic connective tissue of the thick-walledaorta. The necessary function of the CPR 24, 24' is to store blood underhigher pressure, and to later provide that stored blood to themicrocirculation when the external pressures on that microcirculationare reduced.

As depicted in FIGS. 1C and 2D the check valves 22, 22' limits bloodflow in the direction of A, which is from a chamber of a heart into theapparatus 10, 10' via the lumen 11, 11'. The pressure on the bloodwithin the chamber of a heart will be greatest when the surroundingcardiac musculature is in the contracting phase of the cardiac cycle.Because it is during this phase of the cardiac cycle that the externalpressure on the coronary artery microcirculation is also highest, bloodflow through the lumen 11, 11' of the apparatus 10, 10' could belimited. To counteract this tendency, the device 10, 10' is equippedwith a reservoir 24, 24' which stores this pressurized blood flowingfrom a chamber of the heart during the cardiac contraction.

The reservoir, or CPR 24, 24' is schematically illustrated in FIGS 1C,2D. It can be appreciated that the stent 10, 10' is provided with afluid passage 28, 28' in communication with conduit 11, 11'. The passage28, 28' communicates with an expandable volume (or storage chamber) 27,27' defined by a movable wall 31, 31' contained within a fixed housing33, 33'. Springs 29, 29' between wall 31, 31' and housing 33, 33' urgethe wall 31, 31' to move to reduce the size of volume 27, 27'. Thesprings 29, 29' are pre-loaded to exert a force on wall 31, 31' lessthan a force exerted by blood within volume 27, 27' during thecontraction phase of the cardiac cycle, but greater than the forceexerted by blood within volume 27, 27' during the relaxation phase ofthe cardiac cycle.

The apparatus 10, 10' is constructed in a manner which allows blood toflow into the storage chamber 27, 27' of the apparatus 10, 10' throughthe lumen 11, 11' of arm 28, 28' of the apparatus when the cardiacmusculature is contracting. When blood is flowing into the storagechamber 27, 27', the kinetic energy of the flowing blood is converted topotential energy, and stored in 29, 29'. During the relaxation phase ofthe cardiac musculature, the potential energy stored in 29, 29' of theCPR 24, 24' is then re-converted to kinetic energy in the form of bloodflow out of the storage chamber 27, 27' of the apparatus 10, 10' via thelumen 11, 11' of arm 28, 28' of the apparatus.

While the CPR 24, 24' is illustrated with a movable wall 31, 31' andsprings 29, 29' to define a variable volume, other designs can be used.For example, the CPR 24, 24' can be a balloon-like structure. As itfills with blood, the pressure on that blood increases through thestretching of an elastic component of a balloon. In another embodiment,the CPR, 24, 24', can be a hollow bag, made of a material which isinelastic, but impermeable to liquids, and pliable similar to a plasticbag. When the heart contracts, blood is forced through lumen 11, 11' ofarm 28, 28' of the apparatus 10, 10' of the invention into thecollection bag. In this embodiment, the CPR, 24, 24', is physicallylocated in the potential space existing between the fibrous and serouslayers of the pericardium. When the heart expands during the relaxationphase of the cardiac cycle, the increasing heart size within the fixedpericardial sac results in increasing external pressure on thiscollection bag. This increasing external pressure would then force bloodto flow from the collection bag and back through the lumen 11' 11' ofarm 28, 28' of the device 10, 10'. The incorporation of a check valve22, 22' within the anchoring arm 12, 12' of the device 10, 10' wouldlimit the flow of blood out of the device during diastole to thecoronary artery via the lumen 11' 11' of arms 14a, 14a', 16a of thedevice, of the apparatus 10, 10'. Similarly, the incorporation of thecheck valve 26 within the intracoronary arm 16 of the T-shaped apparatus10, when employed with the check valve 22 within the anchor arm 20 ofthe device 10, would limit the flow of blood out of the device duringdiastole to the portion of the coronary artery distal to the bypass sitevia the downstream lumen 11 of arm 14a.

The inner and outer cross-sectional diameters of a coronary arterydecreases with the distance from the arterial origin. Eventually, theartery branches into a number of arterioles, which feed the capillarybed of the coronary arterial microcirculation.

The typical diameter of a lumen of a coronary artery is, in general,species specific; increasing with heart size. In humans, this lumendiameter is dependent upon which artery is being evaluated, but usuallyranges from 2.5 to 4 mm in diameter, and decreases with distance fromthe aortic origin. In the preferred embodiment, the cross-sectionalouter diameter of the intracoronary arms 14, 14', 16 of the device ofthe present invention should effectively approximate the diameter of thelumen of the coronary artery being bypassed, at the bypass site. Thisallows the complete re-approximation of the previously openedsuperficial wall of the coronary artery during surgical closure, withouthigh suture or staple tension resulting. In the most preferredembodiment, the outer diameter of the intracoronary arms 14, 14', 16 ofthe device 10, 10' of the present invention is equal to the diameter ofthe lumen of the coronary artery which is being bypassed, at the bypasslocation. When a CPR is placed, the artery wall may need to be expandedby the addition of a patch, such as dacron, well known in the art.

Also, due to smooth muscle relaxation and secondary vascular dilitation,the cross-sectional diameter of a lumen of a coronary artery willincrease with the oxygen demand of cardiac muscle during times ofstress. The cross-sectional inner diameter of the intracoronary arms 14,14', 16 of the device 10, 10' of the present invention shouldeffectively approximate that diameter necessary to provide adequateblood flow through the downstream lumen of the device 14a, 14a' toeffectively oxygenate the cardiac musculature normally supplied by themicrocirculation of the coronary artery. In the preferred embodiment,the cross-sectional inner diameter of the intracoronary arms 14, 14', 16of the device 10, 10' of the present invention should effectivelyapproximate that diameter necessary to provide adequate blood flowthrough the lumen of the device to effectively oxygenate the cardiacmusculature normally supplied by the microcirculation of the coronaryartery during both times of cardiovascular resting and stress.

Prior to bypass surgery, an initial approximation of the requiredcross-sectional outer diameter of the intracoronary arms 14, 14', 16 ofthe apparatus 10, 10' of the present invention can be gained by standardradiographic techniques. Also, prior to bypass surgery, the appropriateopening pressure of a check valve 22, 22' of the apparatus 10, 10' ofthe present invention can be determined by the dynamic measurements ofcoronary artery pressure, blood flow, and heart chamber pressuresthrough selective catheterization with standard techniques. See MinoruHongo et al., 127 (3) AM. HEART J. 545-51 (March 1994).

During the coronary artery bypass procedure, the most appropriate sizingof the intracoronary arms 14, 14', 16 of the device 10, 10' of thepresent invention can be re-assessed. This can be accomplished byprobing the distal and proximal aspects of the coronary artery at thechosen bypass site with blunt instruments of known outer diameters. Suchsizing by probes is well-known in the literature. To facilitate theeffective matching of the external diameter of the intracoronary arms14, 14', 16 of the device 10, 10' of the present invention to the lumen34 of the coronary artery to be bypassed, an assortment of devices ofthe present invention of various diameters can be available for thesurgeon to select from.

2. The Method of the Present Invention Using the Open Chest Approach

a. General

The method of the present invention is suitable for performing a varietyof surgical cardiac procedures. The procedures may be performedutilizing an open-chest approach, or through less invasive approaches bythe creation of an access space in the chest, or through minimallyinvasive access utilizing intracoronary and intraventricularcatheterization. Dependent on the invasiveness of the approach utilized,the heart can be allowed to pace normally, slowed varying amounts, orstopped completely. A significant period of complete heart stoppage cannecessitate the use of supportive cardiopulmonary bypass.

The method of the present invention for performing a coronary arterybypass procedure will now be described in detail. The patient who is toundergo the procedure can be prepared in a conventional manner forcardiac bypass surgery. The patient preparation, anesthesia utilized,and access route to the coronary circulation, will vary depending uponthe invasiveness of the specific procedure chosen.

b. Preparation for the Procedure

i. General Preparations

Standard techniques of general preparation for open-chest surgery inwhich cardiopulmonary bypass is utilized have been widely reported. See,e.g. LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIALREVASCULARIZATION (1990). In one embodiment of the methods of theinvention where an open-chest procedure and cardiopulmonary bypass isutilized, the patient can be prepared for surgery as outlined by VonSegesser.

General preparations for open-chest surgery in which cardiopulmonarybypass is not utilized have been published by Buffolo et al., 61 ANN.THORAC. SURG. 63-66(1996). In one embodiment of the methods of theinvention where an open-chest procedure without cardiopulmonary bypassis utilized, the patient can be prepared for surgery as outlined byBuffolo.

General preparations for closed-chest surgery, to be performed usingthoracoscopy and where cardiopulmonary bypass is utilized, have beenoutlined by Sterman et al., U.S. Pat. No. 5,452,733 (1995). In oneembodiment of the methods of the invention where a closed-chestprocedure and cardiopulmonary bypass is utilized, the patient can beprepared for surgery as outlined by Sterman.

General preparations for closed-chest surgery to be performed usingthoracoscopy, but where cardiopulmonary bypass is not utilized, havebeen published by Acuff et al., 61 ANN. THORAC. SURG. 135-37 (1996). Inone embodiment of the methods of the invention where a closed-chestprocedure without cardiopulmonary bypass is utilized, the patient can beprepared for surgery as outlined by Acuff.

As presently known to applicant, general preparations forminimally-invasive coronary artery bypass grafting utilizingintracoronary and intraventricular catheterization and withoutcardiopulmonary bypass have not been published. Preparations can includethe sterile scrubbing and draping of at least one groin to permit accessto a femoral artery for catheterization of the coronary vasculature andthe sterile scrubbing and draping of the right superior anterior chestwall to permit access to the innominate artery for catheterization ofthe left ventricle. Further suggested preparations can include thoseoutlined by Sterman and Acuff for thoracoscopic surgery with and withoutcardiopulmonary bypass, respectively.

ii. Anesthesia Prior to and During the Procedure

Most often, the patient will be placed under general anesthesia prior tothe procedure. In one embodiment, standard cardiac operative anesthetictechniques, such as premedication with diazepam, induction with propofoland sufentanil, and maintenance with desflurane can be employed. Onoccasion, less than general anesthesia can be utilized. Less thangeneral anesthesia is well known in the literature. When theinvasiveness of the procedure is minimal, such as when the procedure isto be carried out via intracoronary and intraventricularcatheterization, or when the risks of general anesthesia to theindividual patient outweighs the risks of less than general anesthesiawith regard to the particular procedure planned, less than generalanesthesia can be induced. Selective ventilation of the lungs can beachieved through the placement of a double-lumen endobronchial tubewhich independently provides for the intubation of the left and rightmainstem bronchi. An intraesophageal probe can be placed to facilitatecardiac monitoring and the synchronization of power to the laser, whendeemed useful.

iii. Access to the Heart and Coronary Vasculature for the Procedure

Following preparation, access to the patient's coronary arterialvasculature can be attained through a variety of techniques, dependentupon the route of access chosen.

Von Segesser has reported a method of access to the coronary arterialvasculature when utilizing an open-chest approach and cardiopulmonarybypass. In one embodiment, utilizing an open-chest approach withcardiopulmonary bypass, access to the coronary vasculature can beobtained as reported by Von Segesser.

Buffolo et al. has reported an open-chest approach to the coronaryarterial vasculature when performed without cardiopulmonary bypass. SeeBuffolo et al., 61 ANN. THORAC. SURG. 63-66 (1996). In one embodimentutilizing an open-chest approach without cardiopulmonary bypass, accessto the coronary vasculature can be obtained as reported by Buffolo.

Sterman et al. has reported a method of access to the coronary arterialvasculature when a closed-chest approach with cardiopulmonary bypass isutilized. See Sterman et al., U.S. Pat. No. 5,452,733 (1995). Stermanpositions a plurality of access trocar sheaths along the patient's leftand right anterolateral chest wall. These trocar sheaths provide accessto the coronary vasculature, and allow the temporary repositioning ofthe heart to facilitate the performance of the procedure. Therepositioning is accomplished utilizing grasping tools introducedthrough the appropriate trocar sheaths. Visualization during thisprocedure can be either indirectly via thoracoscopy, or directly via a`window` placed in the left middle anterior chest wall by the surgicalremoval of the fourth rib. Access to the bypass site can therefore beobtained by following the techniques outlined by Sterman. Theinstruments to be used in the procedure can also be similar to thosedescribed by Sterman.

Acuff et al. has described a method of access to the coronary arterialvasculature when a closed-chest approach without cardiopulmonary bypassis utilized. See Acuff et al., 61 ANN. THORAC. SURG. 135-37 (1996).Similar to the techniques of Sterman, Acuff positions a plurality ofaccess trocar sheaths along the patient's left and right anterolateralchest wall. Also similar to Sterman, Acuff surgically establishes anaccess space, or window in the left anterior chest wall through theremoval of the left fourth rib cartilage. The trocar sheaths, in concertwith this window, allow the temporary repositioning of the heart, andaccess to the coronary arterial vasculature. Visualization during thisprocedure can be either indirectly via thoracoscopy, or directly via thewindow. Access to the bypass site can therefore be obtained by followingthe techniques outlined by Acuff. The instruments to be used in theprocedure can also be similar to those described by Acuff.

Access to a chamber of a heart and a coronary artery when the bypass isperformed through the minimally invasive approach of intracoronary andintraventricular catheterization can be obtained as follows. Access to acoronary artery can be obtained by the introduction of a catheter intothe left or right femoral artery through an arterial cut down procedure.The catheter can then be fed retrograde past the descending aorta,through the ascending aorta, and into the coronary artery by standardcatheterization techniques. In a preferred embodiment, access to achamber of the left side of a heart can be obtained by the introductionof a catheter into the innominate artery, also through an arterial cutdown procedure. In the most preferred embodiment, access to the leftventricle is obtained by the introduction of a catheter into theinnominate artery and the advancement of this catheter into the leftventricle. In this embodiment, the catheter is advanced through theascending aorta, past the aortic valve. and into the left ventricle.Techniques by which the left ventricle is catheterized are well known inthe literature.

iv. The Procedure

In the coronary artery bypass graft procedures of the present invention,a chamber of a heart provides blood to a coronary artery. The method ofthe present invention can accomplish this by establishing one or morechannels through the wall of a chamber of a heart which lead directlyfrom a chamber of a heart into a coronary artery at a site distal to thenarrowing or blockage. The methods of the invention in variousembodiments can achieve the establishment of such a channel or channelsthrough a variety of techniques.

Referring now to FIGS. 4, 5, 6, 7, 8, and 9, an exemplary open-chestprocedure, to include cardiopulmonary bypass, by which a coronary arterybypass procedure may be accomplished will be described. The open-chestapproach affords maximal access to, and visualization of, the coronaryvasculature; although at the expense of injury to normal tissue.

Through the methods of the present invention, the device 10, 10' of thepresent invention, which provides blood from a chamber of a heart 43directly into a coronary artery 30, is placed. To illustrate theinvention, only placement of stent 10 is discussed. It will beappreciated that stent 10' can be similarly placed. In addition,examples will be limited to the embodiment of the apparatus of theinvention as illustrated in FIG. 2A.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

First, the chest cavity is entered, and pericardium 52 incisedanteriorly, to expose a coronary artery 30 (having an obstruction 34) tobe bypassed. This is illustrated in FIG. 4.

Second, cardiopulmonary bypass is initiated by a variety of standardtechniques as outlined by George Silvay et al., Cardiopulmonary Bypassfor Adult patients: A Survey of Equipment and Techniques, 9(4) J.CARDIOTHORAC. VASC. ANESTH. 420-24 (Aug. 20, 1995).

Third, the heart is slowed and/or stopped by a variety of standardtechniques. One standard technique is to electrically induce ventricularfibrillation. Another standard technique is warm or cold bloodcardioplegia, delivered antegrade or retrograde, and intermittent orcontinuous, as outlined by Gerald D. Buckberg, Update on CurrentTechniques of Myocardial Protection, 60 ANN. THORAC. SURG. 805-14(1995).

Fourth, the heart is inspected and coronary arteries identified. Thenarrowed or occluded coronary artery 30 can be visually identified, andan appropriate site distal or downstream from the occlusion 34 chosen.

Fifth, blood flow through the target coronary artery 30 is halted bystandard techniques. For example, standard techniques include clampingwith a arterial clamp. Alternatively, the flow of blood within thecoronary artery 30 can be halted by forming a loop around the artery 30with suture either proximally, or both proximally and distally, andapplying appropriate tension on the suture or sutures, or tying thesuture or sutures.

Sixth, depending on the degree of exposure deemed necessary, theepicardium overlying the coronary artery at the selected bypass site isincised. This exposure can facilitate locating the lumen of the coronaryartery 30 via palpation.

Seventh, as shown in FIG. 5, the superficial wall 36 of the coronaryartery 30 is longitudinally incised by standard techniques, such asincision with a scalpel, electrosurgical cutting device, or similartool; taking care not to damage the deep wall of the artery. Thisinitial incision can be lengthened, if necessary, to accommodate theintracoronary arms 14, 14', 16 of the device 10, 10', using standardtools such as fine angled scissors.

Eighth, a channel, 50, is initiated into the deep coronary arterialwall, 40, and into the musculature, 42, of a chamber of a heart. In thepreferred embodiment, a chamber of a heart is a chamber of the left sideof the heart. In the most preferred embodiment, a chamber of a heart isthe left ventricle. The channel 50 can be initiated by standardtechniques such as awl punching, incising, use of a laser, or the like.The channel is then extended into the chamber of a heart, in this casethe left ventricle, 44, by standard techniques (such as punching with atrocar 46, incising with a scalpel blade, electrosurgical cutting withan electrosurgical cutting tool, laser or radiofrequency ablation, bluntdissection, etc.).

Ninth, once a channel extending through the entire thickness of a wall42 of a chamber of a heart is formed, it can be systematically sized bythe passage of standard probes.

Tenth, through palpation, inspection, and probing of the distal andproximal coronary artery lumen 48, a device 10, 10', of the presentinvention of appropriate dimensions is selected, as outlined above.

Eleventh, as illustrated in FIGS. 7 and 8, the anchor arm 12, 12' of theapparatus of the present invention 10, 10' is inserted into the formedchannel 50. The one or two remaining arms 14, 14', 16 of the device 10,10' are then seated within the lumen 48 of the coronary artery 30.

Twelfth, as shown in FIG. 9, the longitudinal incision 38 previouslyincised in the anterior wall 36 of the coronary artery 30 is surgicallyre-aproximated. The re-approximation can be performed by a number ofconventional techniques, including suturing 52, laser welding,microstapling, and the like.

Thirteenth, the clamps or sutures closing off blood flow to the coronaryartery are released.

Fourteenth, contractions of the heart, are reinitiated by standardelectrostimulation or the reversal of cardioplegia.

Fourteenth, the patient is slowly weaned from cardiopulmonary bypass bystandard techniques.

Fifteenth, the pericardium, sternum, and overlying skin of the chest isre-approximated and surgically closed by standard, conventionaltechniques.

Sixteenth, anesthesia is reversed and the patient revived by standardtechniques.

D. Embodiments with the Closed Chest Approach

1. The Apparatus of the Present Invention for Use in the Closed OpenChest Approach

A closed chest approach according to the method of the present inventionmay use the stent 10, 10' as described above. Such a procedure will nowbe described. Following this description, a closed chest approach usingalternative embodiments of the apparatus of the invention will bedescribed.

2. The Method of the Present Invention Using the Closed Chest Approach

An exemplary closed-chest procedure, without cardiopulmonary ypass, bywhich a coronary artery bypass may be accomplished will now bedescribed. The closed-chest approach is less invasive than theopen-chest approach, although providing the surgeon with somewhat poorervisualization and limited direct access to both the chambers of theheart and coronary artery bypass site.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

First, a plurality of access trocar sheaths is positioned anterior andlaterally along the left and right chest walls as outlined by Acuff etal.

Second, a space in the left low anterior chest wall is formed by removalof the fourth rib cartilleage, as outlined by Acuff et al. In thisembodiment, the heart and coronary artery can be both directly viewedvia this space or window, as well as indirectly visualized via athoracoscope.

Third, a standard pericardiotomy is performed using a scalpel orelectrosurgical cutting tool introduced through the left lateral chesttrocar sheaths while viewing under thoroacoscopy. The pericardium can beexcised and either spread open, or removed from the thoracic cavity asoutlined by Acuff et al.

Fourth, if necessary, the can be rotated within the mediastinum. Directaccess and visualization through the formed chest wall space can requirerotation of the heart. Rotation of the heart can be accomplished by thegrasping of the heart by tools inserted through access trocar sheathslocated along the left and right chest wall as described by Sterman etal. Alternatively, traction on sutures placed in the pericardium candistract the heart allowing appropriate direct visualization of the areato be bypassed as described by Acuff et al.

Fifth, once the coronary artery to be bypassed is identified andwell-visualized; snare sutures of 5-0 polypropylene are placedproximally and distally to the target area as described by Acuff et al.

Sixth, the heart rate can be slowed to approximately 40 beats/minute bythe intravenous administration of esmolol or diltiazem to minimizemotion within the operative field as described by Acuff etal.Nitroglycerin and heparin can also be administered to reduce cardiacischemia and prevent clotting respectively as outlined by Acuff et al.

Because cardiopulmonary bypass is omitted in this embodiment,intermittent coronary artery occlusion to induce ischemicpreconditioning, as well as transesophageal echocardiography to reviewcardiac wall motion changes, can be utilized as described by Acuff etal. The epicardium can be incised over the area selected for bypass andthe anterior surface of the artery cleared under direct visualizationthrough the space or window, or via remote instruments inserted throughthe trocar sheaths under thoracoscopic guidance.

Seventh, in situations where the coronary artery can be directly viewed,the lumen 48 of the coronary artery is identified by palpation. Eitherunder direct visualization, or under thoracoscopic guidance and usinginstruments manipulated through the trocar sheaths, the superficial wall36 of the coronary artery is then longitudinally opened. As above, careis taken to leave the deep wall 40 of the artery undamaged. The incision38 can be enlarged, as necessary, to accommodate the intracoronary arms14, 14', 16 of the device 10, 10' of the present invention using fineangled scissors. This enlargement can be performed with standardsurgical scissors under direct viewing through the window, or via othersurgical instruments remotely manipulated following their insertionthrough the trocar sheaths.

Eighth, a channel 50 through the heart wall is initiated by incising orlaser ablating into the deep wall 40 of the coronary artery. This alsocan be performed by standard surgical tools under direct viewing, or bythe remote manipulation of specialized instruments introduced throughthe trocar sheaths and viewed thoracoscopically. The channel 50 is thenextended through the deep coronary arterial wall 40, through underlyingcardiac musculature 42, and into the underlying chamber of the heart 44by incising with a scalpel or electrosurgical cutting blade, laserablation, blunt dissection, or the like. In the preferred embodiment, achamber of a heart 44 is one of the two chambers of the left side of theheart. In the most preferred embodiment, a chamber of a heart 44 is theleft ventricle.

Ninth, the channel 50 extending through the entire thickness of amuscular wall 42 can be systematically sized by the passage of standardmeasuring probes. These standard measuring probes, with fixed and knowntip diameters, can be similarly used to size and determine the proximaland distal patency of the coronary artery being bypassed.

Tenth, through direct and/or thoracoscopic inspection of the coronaryartery lumen 48, or by probing as outlined above, an appropriatelydimensioned device 10, 10' of the present invention is selected. As inthe case of the open-chest approach (outlined above), an array ofdevices 10, 10' of various sizes can be available for the operation.

Eleventh, either under direct control and visualization, or by indirectmanipulation and thoracoscopic viewing, the anchoring arm 12, 12' of theapparatus 10, 10 of the invention is inserted into the formed channel50. By similar techniques the remaining intracoronary arm or arms 14,14', 16 of the apparatus 10, 10' are seated within the lumen 48 of thecoronary artery 30 being bypassed. In one embodiment where the procedureis performed under thoracoscopic viewing, the device 10, 10' can beintroduced into the cardiac cavity through the space or windowpreviously formed within the anterior inferior aspect of the left chestwall. In this embodiment, the device 10, 10' can be grasped, onceintroduced into the chest cavity, by surgical instruments insertedthrough the trocar sheaths and remotely manipulated into position. Inthis manner the anchor arm 12, 12' of the device 10, 10' is theninserted into the channel formed 50 via the remote manipulation of theseinstruments.

Twelfth, the incision present in the superficial wall 38 of the coronaryartery 30 is closed by conventional surgical techniques such assuturing, laser welding, microstapling, and the like. When closure is byindirect thoracoscopic versus direct viewing, suturing, laser welding,microstapling and the like can be accomplished by utilizing surgicalinstruments remotely manipulated following their introduction throughthe trocar sheaths.

Thirteenth, upon completion of placement of the device 10, 10' of thepresent invention, the heart, if rotated, can be returned to its normalorientation.

Fourteenth, all heart manipulating devices are removed from the chestcavity.

Fifteenth, contractions of the heart can be allowed to return to theirnormal resting rate by the discontinuation of intravenous esmolol anddiltiazem, if utilized.

Sixteenth, the pericardium 52 is partially or completelyre-approximated. An external drain can be placed inside the pericardium,as needed, as described by Acuff et al.

Seventeenth, the trocar sheaths are removed, and all thoracic puncturessurgically repaired in a conventional manner.

Eighteenth, anesthesia is reversed and the patient revived by standardtechniques.

E. Embodiments with the Catheter-Controlled Approach

Referring now to FIGS. 10, 11, 12, 13, 14, 15, and 16, an exemplarycoronary artery bypass procedure performed through catheterization willbe described. This approach allows no direct visualization of thecoronary vasculature, although the chamber of the heart could beindirectly visualized during the procedure by equipping theintraventricular catheter with a standard fiber-optic device, ifdesired. Because the procedure is performed through catheters introducedremotely, normal tissue injury is minimized.

Preparation for the procedure, and anesthesia prior to and during theprocedure, is outlined above.

In the embodiment to be described, cardiopulmonary bypass isunnecessary. However, the procedure would be in no way limited ifcardiopulmonary bypass were performed.

First, an intracoronary catheter 120 (FIG. 10) is inserted via anincision in the groin 126 and advanced within the femoral artery 124.Through continued advancement within the descending aorta 128, and theascending aorta 122, the coronary artery 30 is entered.

Dependent on the degree of narrowing or occlusion of the coronaryartery, standard angioplasty, atherectomy, or some similar procedure canbe optionally performed if passage of the catheter tip 136 (FIG. 11A) ishindered. Angioplasty, arthrectomy, and the like could optionallyprecede the catheter-controlled bypass procedure.

If desired, the heart may be slowed while catheterizing the coronaryvasculature, during the construction of a channel or channels 50 leadingfrom a chamber of a heart 44 into a lumen of a coronary artery 30itself, or both. Such slowing can improve visualization of the cathetersas facilitated by fluoroscopy or the alternative radiologic techniquesby which the procedure can be performed. Standard pharmacologic methods,as described above, to slow the heart are well known in the literature.

Second, the intracoronary catheter 120 is advanced within the coronaryarterial vasculature tree to the target location through standardcatheter manipulation techniques. The proper location of theintracoronary catheter tip 136 in relation to the targeted bypass sitecan be determined through standard radiographic techniques.

Third, as shown in FIGS. 11A-11C, a balloon 130 located on the distalend of the intracoronary catheter 120 is inflated (FIG. 11B). Inflationof the balloon 130 causes a stent 134 located circumferentiallysurrounding the balloon 130 to be seated against the coronary arterialwalls 36, 40. The stent 134 is a hollow expandable stent having acut-out area 135 along the cylindrical wall of the stent 134, forreasons that will become apparent. The stent 134 is positioned atplacement within the coronary artery in a manner that the cut-out 135 isjuxtaposed against the deep wall 40 of the coronary artery 30 uponinflation of the intracoronary catheter balloon 130.

Fourth, the balloon 130 is deflated (FIG. 11C) and the catheter 120withdrawn into the ascending aorta 122 leaving the expanded stent 134 inplace.

Fifth, an intraventricular catheter 140 is inserted into the innominateartery 144 via an incision in the anterior superior right chest wall 142as shown in FIG. 12. The intraventricular catheter 140 is advanced in aretrograde fashion through the ascending aorta 22, and into the chambersof the left side of the heart. By continued advancement, theintraventricular catheter 140 is extended past the semilunar valves 148and into the left ventricle 44. Throughout the procedure, the locationof the intraventricular catheter 140 within a chamber of a heart 44 canbe ascertained by either indirect visualization employing standardfiber-optic instrumentation inherent to the intraventricular catheter,or and/or by standard radiographic techniques.

Sixth, a channel 50 can be ablated (FIGS. 13A-13B) through both a wallof a chamber of a heart 42 and the deep wall of a coronary artery 40utilizing an ablating tip 132. Such ablating devices are well known inthe literature and can include a laser, a radiofrequency device, or thelike. Power to the ablating tip 132 can be synchronized via theintraesophageal probe such that ablation occurs at a recurring aspect ofthe cardiac cycle. Such synchronization of devices to physiologicalfunction is well-known in the literature. The ablation can be indirectlyobserved via fiber optics associated with the intraventricular catheter140. Alternatively, the location of the ablating tip 132 can bedetermined by standard radiographic techniques.

Seventh, once a channel 50 through the heart chamber wall 42 is formed,the intracoronary catheter 120 is re-advanced into the coronary artery30.

Eighth, the balloon 130 on the distal end of the intracoronary catheter120 is re-inflated upon reaching the target bypass site, as illustratedin FIGS. 14A and 14B. Inflation of the intracoronary catheter balloon130 seals the formed channel 50 so that blood is prevented from flowingfrom the coronary artery lumen 48, through the formed channel 50, andinto a chamber of the heart 44. Note, though, that the inflation of theintracoronary catheter balloon 130 still allows blood to perfuse thedownstream portion of the coronary artery 30. This is because theintracoronary catheter 120 is equipped with channels 138 which allowblood to pass internally within the intracoronary catheter 120 from theupstream portion of the coronary artery 30, and to exit the catheterinto the downstream portion of the coronary artery 30.

Ninth, the ablating catheter 140 is removed from the body completely.

Tenth, a second intraventricular catheter 160 is inserted into theinnominate artery 144 at the arterial cut-down site 142, as shown inFIG. 12. The intraventricular catheter 160 is next advanced in aretrograde fashion into the ascending aorta 22. By continuedadvancement, the intraventricular catheter 160 is finally extended pastthe semilunar valves 148 and into the left ventricle 44.

This intraventricular catheter is equipped with a inflatable balloon 60on the catheter's distal end, and a stent-forming device 61circumferentially surrounding the balloon 60 on the catheter's distalend (FIGS. 14A-14D).

The stent forming device 61 is a spiral sheet shown seperately in FIGS.15A and 15B. Initially, the device 61 is a sheet formed in a spiralshape as shown in FIG. 15A to present a reduced diameter smaller thanthe diameter of the formed channel 50. In response to expanding forces(e.g., expansion of a balloon 60 within device 61), device 61 expands toa cylinder as shown in FIG. 15B. Interlocking tabs 61a and recesses 61bon opposing edges of the device 61 define a locking mechanism 62 toretain the device 61 in a cylindrical shape. The cylindrical shape ofdevice 61 after expansion of the balloon 60, as shown in FIG. 15B, islarger in diameter than the spiral shape of device 61 prior to expansionof the balloon 60, as shown in FIG. 15A. The device 61 as expanded issized to be retained within the formed channel 50 upon expansion.

Throughout this portion of the procedure, the location of this secondintraventricular catheter 160 within a chamber of a heart 44 can beascertained by either indirect visualization employing standardfiber-optic instrumentation inherent to the second intraventricularcatheter, or and/or by standard radiographic techniques.

Eleventh, the tip 180 (FIG. 14A) of the second intraventricular catheter160 is introduced into and advanced within the formed channel 50.

Twelfth, with the tip 180 of the second intraventricular catheter 160near or abutting the side of the intracoronary catheter balloon 130, aballoon 60 surrounding circumferentially the tip of the secondintraventricular catheter 160, is inflated. As shown in FIGS. 14C and14D, inflation of the balloon 60 causes the device 61 locatedcircumferentially around the balloon 60 located on the end of the secondintraventricular catheter 160 to become seated against the walls of theformed channel 50.

As shown in FIG. 16, the device 61, is locked into the cylindricalposition when the underlying balloon 60 is inflated by an interlockingmechanism 62 constructed as part of the device 61.

Thirteenth, the balloon 60 on the intraventricular catheter tip isdeflated, and the catheter removed from the body, as shown in FIG. 14D.

Fourteenth, a third intraventricular catheter 70 is inserted at theinnominate artery access site 142. This third intraventricular catheter70 is then advanced in a retrograde fashion into a chamber of the leftside of a heart, as outlined above.

This third intraventricular catheter 70 is equipped with a hollow tube71 on its distal tip which can interlock to the device 61 previouslyplaced within the formed channel 50, as shown in FIGS. 17A and 17B.

Fifteenth, the hollow tube 71 is forwarded within the formed channel 50,and interlocked to the device 61. In one embodiment, the hollow tube 71can partially insert into the device 61 previously seated within theformed channel 50.

The hollow tube 71 can, but may not necessarily, be equipped with aone-way check valve 74 to limit blood flow to ther direction of arrow C.An array of such hollow tubes 71 of various dimensions can be availableto the surgeon at the operative procedure.

Sixteenth, the balloon 130 on the end of the intracoronary catheter 120is deflated.

Seventeenth, angiographic dye can be introduced into a chamber of theheart through a port internal to the third intraventricular catheter 71.The introduction of angiographic dye can allow the blood flow to bevisualized under fluoroscopy, digital subtraction angiography, orsimilar standard techniques. By such radiographic examination, bloodflow directly from a chamber of a heart into a coronary artery can beascertained. In cases where a check valve 74 is utilized, theuni-directional flow from a chamber of a heart and into a coronaryartery, in the direction of arrow C, can be verified.

Eighteenth, the third intraventricular catheter 70 is withdrawn from thebody through the innominate incision site 142.

Nineteenth, the intracoronary catheter 120 is withdrawn from the bodythrough the femoral incision site 126.

Twentieth, the sites of the innominate incision 142 and femoral incision126 are surgically re-approximated through standard closure techniques.

Twenty-first, anesthesia is reversed and the patient revived by standardtechniques.

Changes and Modifications

Although the foregoing invention has been described in detail by way ofillustration and example, for purposes of clarity of understanding, itwill be obvious that changes and modifications may be practiced withinthe scope of the appended claims.

What is claimed is:
 1. An apparatus for use in a coronary artery bypassprocedure at a coronary vessel disposed lying at an exterior of a heartwall, the apparatus comprising;a hollow blood flow conduit having afirst end adapted to be inserted into and retained within the heart wallof a heart chamber containing oxygenated blood with an opening of thefirst end in blood-flow communication with blood contained within thechamber; the conduit having a second end adapted to be connected to thecoronary vessel with an opening of the second end in blood flowcommunication with a lumen of the coronary vessel such that the secondend can be substantially axially aligned with the vessel; the conduitdefining a blood flow path between the openings of the first and secondends; and wherein the conduit includes a reservoir for accumulatingblood from the conduit during periods of high blood pressure and fordischarging accumulated blood into the conduit during periods of lowblood pressure.
 2. An apparatus for use in a coronary artery bypassprocedure at a coronary vessel disposed lying at an exterior of a heartwall, the apparatus comprising;a hollow blood flow conduit having afirst end adapted to be inserted into and retained within the heart wallof a heart chamber containing oxygenated blood with an opening of thefirst end in blood-flow communication with blood contained within thechamber; the conduit having a second end adapted to be connected to thecoronary vessel with an opening of the second end in blood flowcommunication with a lumen of the coronary vessel such that the secondend can be substantially axially aligned with the vessel; the conduitdefining a blood flow path between the openings of the first and secondends; and wherein the blood flow path closes at least once during acycle of the heart.
 3. An apparatus according to claim 2 wherein theconduit includes a valve to close during diastole.
 4. A method forperforming a coronary bypass procedure at a coronary vessel disposedlying at an exterior of a heart wall of a heart having a heart chamber,the method comprising:inserting a hollow conduit through the heart wallwhere the conduit defines a blood flow path between a heart chamberopening and a vessel opening and with the heart chamber opening of theconduit in blood flow communication with the heart chamber; placing thevessel opening of the conduit to direct blood to flow from the bloodflow path into the vessel in a flow direction generally parallel with anaxis of the vessel.
 5. A method according to claim 4 further comprisingplacing the vessel opening facing away from an obstruction which atleast partially obstructs blood flow through the vessel.
 6. A methodaccording to claim 4 wherein the blood flow path is formed by placingthe conduit through a deep wall of the coronary vessel.
 7. A methodaccording to claim 4 wherein the coronary vessel is a coronary artery.8. A method according to claim 4 comprising closing the blood flow pathonce per cycle of the heart.
 9. A method according to claim 8 whereinthe blood flow path is closed during diastole.
 10. A method according toclaim 4 wherein at least an end of the conduit at the vessel opening isan expandable open structure adapted to be expanded within the coronaryvessel, the method including expanding the open structure in thecoronary vessel.
 11. A method according to claim 4 wherein at least anend of the conduit at the heart chamber opening includes a structuralportion having sufficient rigidity to hold the myocardium open duringdiastole and systole and further including a fabric liner extendingalong a length of the structural portion, the method including placingthe structural portion in the myocardium with the heart chamber openingin communication with the heart chamber.
 12. A method according to claim10 wherein an end of the conduit at the heart chamber opening is anexpandable member adapted to be expanded within the myocardium, themethod including expanding the expandable member in the myocardium. 13.A method according to claim 4 wherein the heart chamber is a leftventricle.
 14. A method according to claim 13 wherein the coronaryvessel is a coronary artery.
 15. A method according to claim 14including blocking blood from flowing from the conduit in a proximaldirection in the coronary artery.
 16. A method according to claim 15including placing the heart chamber opening protruding into the leftventricle.
 17. A method according to claim 4 wherein said conduit ismaintained open to blood flow during both systole and diastole.
 18. Amethod according to claim 4 wherein said conduit is selected to closeonce per heart cycle.
 19. A method according to claim 4 wherein saidconduit is selected to have a length in the myocardium which varies inresponse to expansion and contraction of the myocardium.